update readme

Author: guo-yong-zhi

README.md

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 # LanguageIdentification.jl
+
+[![docs](https://img.shields.io/badge/docs-dev-blue.svg)](https://guo-yong-zhi.github.io/LanguageIdentification.jl/dev) [![CI](https://github.com/guo-yong-zhi/LanguageIdentification.jl/actions/workflows/ci.yml/badge.svg)](https://github.com/guo-yong-zhi/LanguageIdentification.jl/actions/workflows/ci.yml) [![CI-nightly](https://github.com/guo-yong-zhi/LanguageIdentification.jl/actions/workflows/ci-nightly.yml/badge.svg)](https://github.com/guo-yong-zhi/LanguageIdentification.jl/actions/workflows/ci-nightly.yml) [![codecov](https://codecov.io/gh/guo-yong-zhi/LanguageIdentification.jl/graph/badge.svg?token=lwDSoRUTmH)](https://codecov.io/gh/guo-yong-zhi/LanguageIdentification.jl)
 # Installation
 ```julia
 import Pkg; Pkg.add("LanguageIdentification")
-```
+```
+# Usage
+After loading the package, initialization is required. Different parameters have different balances among accuracy, speed, and memory usage. See the documentation for details. 
+```julia
+using LanguageIdentification
+LanguageIdentification.initialize()
+```
+Currently, `LanguageIdentification.jl` supports the identification of 50 languages. You can check them with the following command, where the language is represented by the [ISO 639-3](https://en.wikipedia.org/wiki/ISO_639_macrolanguage) code.
+```julia
+LanguageIdentification.supported_languages()
+```
+```julia
+ ["ara", "bel", "ben", "bul", "cat", "ces", "dan", "deu", "ell", "eng", "epo", "fas", 
+ "fin", "fra", "hau", "hbs", "heb", "hin", "hun", "ido", "ina", "isl", "ita", "jpn", 
+ "kab", "kor", "kur", "lat", "lit", "mar", "mkd", "msa", "nds", "nld", "nor", "pol", 
+ "por", "ron", "rus", "slk", "spa", "swa", "swe", "tat", "tgl", "tur", "ukr", "vie", 
+ "yid", "zho"]
+```
+This package provides a simple interface to identify the language of a given text. The package exports two functions:
+- `langid`: returns the language code of the tested text.
+- `langprob`: returns the probabilities of the tested text for each language.
+```julia
+langid("This is a test.")
+```
+```julia
+"eng"
+```
+```julia
+langprob("这是一个测试。", topk=3)
+```
+```julia
+["zho" => 0.157798836477618,
+"mar" => 0.11718444394383595,
+"ben" => 0.10440699125820749,]
+```
+# Benchmark
+todo